x86: add check for node passed to node_to_cpumask, v3

  * When CONFIG_DEBUG_PER_CPU_MAPS is set, the node passed to
    node_to_cpumask and node_to_cpumask_ptr should be validated.
    If invalid, then a dump_stack is performed and a zero cpumask
    is returned.

v2: Slightly different version to remove a compiler warning.
v3: Redone to reflect moving setup.c -> setup_percpu.c

Signed-off-by: Mike Travis <travis@sgi.com>
Cc: Vegard Nossum <vegard.nossum@gmail.com>
Cc: "akpm@linux-foundation.org" <akpm@linux-foundation.org>
Cc: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 23 insertions, 3 deletions

diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c
index 7068f95cccc6..43aca2de624a 100644
--- a/arch/x86/kernel/setup_percpu.c
+++ b/arch/x86/kernel/setup_percpu.c
@@ -346,6 +346,10 @@ int early_cpu_to_node(int cpu)
         return per_cpu(x86_cpu_to_node_map, cpu);
 }
 
+
+/* empty cpumask */
+static const cpumask_t cpu_mask_none;
+
 /*
  * Returns a pointer to the bitmask of CPUs on Node 'node'.
  */
@@ -358,13 +362,23 @@ cpumask_t *_node_to_cpumask_ptr(int node)
                 dump_stack();
                 return &cpu_online_map;
         }
-        BUG_ON(node >= nr_node_ids);
-        return &node_to_cpumask_map[node];
+        if (node >= nr_node_ids) {
+                printk(KERN_WARNING
+                        "_node_to_cpumask_ptr(%d): node > nr_node_ids(%d)\n",
+                        node, nr_node_ids);
+                dump_stack();
+                return (cpumask_t *)&cpu_mask_none;
+        }
+        return (cpumask_t *)&node_to_cpumask_map[node];
 }
 EXPORT_SYMBOL(_node_to_cpumask_ptr);
 
 /*
  * Returns a bitmask of CPUs on Node 'node'.
+ *
+ * Side note: this function creates the returned cpumask on the stack
+ * so with a high NR_CPUS count, excessive stack space is used.  The
+ * node_to_cpumask_ptr function should be used whenever possible.
  */
 cpumask_t node_to_cpumask(int node)
 {
@@ -374,7 +388,13 @@ cpumask_t node_to_cpumask(int node)
                 dump_stack();
                 return cpu_online_map;
         }
-        BUG_ON(node >= nr_node_ids);
+        if (node >= nr_node_ids) {
+                printk(KERN_WARNING
+                        "node_to_cpumask(%d): node > nr_node_ids(%d)\n",
+                        node, nr_node_ids);
+                dump_stack();
+                return cpu_mask_none;
+        }
         return node_to_cpumask_map[node];
 }
 EXPORT_SYMBOL(node_to_cpumask);